With the widespread proliferation of personal computers, images are conventionally input as electronic data by an image input apparatus such as a digital camera and color scanner, and the input images are displayed, checked, edited, processed or modified according to various purposes of use by an image display apparatus such as a CRT and LCD and output by an image output apparatus such as a color printer. Recently, it is also often the case that images taken by a digital camera are directly output by a color printer without displaying them on a color monitor. Furthermore, CG images created on a computer are also output to a color printer, that is, a way of use without requiring any image input apparatus.
When images are handled among different input/output apparatuses such as a digital camera, color scanner, color monitor and color printer as shown above, their color reproduction characteristic and color reproduction range vary from one apparatus to another. Thus, a technique called a “color management system” (hereinafter referred to as “CMS”) which matches color reproductions among different image processing apparatuses has emerged. The CMS consists of a device profile that describes color reproduction characteristics of various image processing apparatuses and a color matching method that performs color conversion, etc. Realizing consistent color reproduction among various image processing apparatuses requires the accuracy of the above-described device profile and color matching method to be improved, and therefore the device profile is updated as appropriate.
Here, there is a plurality of color conversion methods according to the contents of images and the purpose of color conversion, etc. For example, there are a method of matching a monitor display and printer output, a method of converting print output in a preferred manner, a method of converting the print output as clearly as possible or in such a way that the color zones of the printer can be used as widely as possible, etc. The above-described color conversion methods also include a color conversion method which uses corresponding colors for output color signals corresponding to input color signals.
However, in the above-described examples, the device profile is not necessarily updated on appropriate occasions. Instead, the device profile is updated periodically, or, in the case of color matching between the monitor and device, for example, it is updated when the user deems it necessary to update by comparing display colors on a color monitor and an output result from a color printer when matching the monitor and printer, and thus there are no clear criteria as to whether or not to update the profile. Moreover, the criteria are subjective and ambiguous, dependent on a decision based on perception by the human eyes and not based on quantified criteria. Japanese Patent Laid-Open No. 11-232073 discloses details on updating a device profile for improving the accuracy of matching among various color image processing apparatuses, but it again discloses that the device profile is updated under the user's visual check, failing to provide clear criteria or quantification.
On the other hand, there are also cases where it is objectively decided whether or not to update the profile. However, in this case of monitor matching, attention is simply focused on a color difference in colorimetric values between the color monitor display color and color printer output color. Thus, according to a color conversion method whereby matching is performed between light source colors displayed on a color monitor, etc. and object colors output to a color printer, etc., how the respective colors appear varies from one color to another and even if colorimetric values are matched, they do not appear as the same color, in other words, the above-described color conversion method does not employ criteria that reflect how colors appear in the human eyes and has a problem that it cannot precisely decide the accuracy in color conversion. On the other hand, the method of converting printed objects in a preferred manner has difficulty in quantifying the subjective content of such preferences and has a problem that it is unable to precisely decide the accuracy in color conversion.
The present invention has been implemented taking into account the problems described above and it is an object of the present invention to provide an image processing apparatus, image processing method and storage medium that seeks to achieve color matching accuracy according to objective criteria based on human visual characteristics.
It is another object of the present invention to provide an image processing apparatus, image processing method and storage medium capable of exactly verifying the color conversion accuracy for each color conversion content, updating a device profile as appropriate and performing color conversion accurately.